RU2531097C1 - Method of determining static and oscillatory aerodynamic derivatives of models of aircrafts and device for its implementation - Google Patents

Abstract

FIELD: aviation.

SUBSTANCE: testing is carried out both in the flow and without flow in the aerodynamic tunnel, the model by strain-gage weighers and holders are mounted in the movable support device, the model is oscillated with a fixed frequency and small amplitude alternatively about axes Ox, Oy and Oz. Then the load acting on the model is measured in time, and its angular position, the inertia and weight loads are subtracted, in the process of testing the model together with the holder and the strain-gage weighers are turned by fixed angles of heel, the experimental results with fluctuations relative to the axes Oy and Oz are treated together. The device comprises a turning table in the working part of the aerodynamic tunnel, the stand on the turning table, the movable L-shaped frame, the holder of the model with strain-gage weighers, mounted in the bearing assembly of the frame, the connected by rods with the frame and the holders, the sensors of the frame rotation angle and the holders. The holder is made with the ability of remotely controlled unit at a predetermined angle of heel using the mechanism consisting of a housing mounted on the bearing assembly of the frame coaxially to the holder by means of bearings, the electric gear motor, the output shaft with elastic drive-pinion connected to the free end of the holder, the pneumatic brake of the disc, the additional sensor of the mounting angle of the holder in roll, which is spaced from the axis of the holder and is connected to the drive-pinion, outside the housing is provided with a lever-clip for fixing mechanism relative to the frame and for connection by the rod with the drive.

EFFECT: increasing the capabilities of determining static and oscillatory aerodynamic derivatives of aircraft models in the aerodynamic tunnel in the presence of slip angle in the whole range of angles of attack.

2 cl, 7 dwg

Description

The invention relates to the field of experimental aerodynamics of aircraft.

The importance of determining static and unsteady aerodynamic derivatives of aircraft in a wide range of angles of attack and slip is due, first of all, to the need to ensure the safe operation of the aircraft, in particular to prevent the aircraft from stalling and falling into a tailspin. According to world statistics, more than half of accidents and disasters occur precisely for this reason (General aviation. Recommendations for designers. Edited by Prof. V.G. Mikeladze, M., TsAGI, 2001, p.213 )

From the existing level of technology there is a known method for determining static and non-stationary aerodynamic derivatives of aircraft models in a wind tunnel by the forced-oscillation method, in which the model is installed in a movable support device using tensile weights and holders, the model is oscillated with a fixed frequency and small amplitude alternately relative to the connected axes Ox, Oy and Oz, measure in time the aerodynamic loads acting on the model and its angular position (G.S.Bushgens, R.V. Studnev , Aerodynamics of an airplane. Dynamics of longitudinal and lateral movement. M., Mechanical Engineering, 1979, p. 32-34). The disadvantage of this method is the inability to determine longitudinal static and unsteady aerodynamic derivative models of aircraft and yaw characteristics at non-zero sliding angles if the model’s angle of attack is not zero, as well as roll characteristics at non-zero sliding angles the entire range of angles of attack of the model.

Closest to the claimed technical solution is a method for determining static and non-stationary aerodynamic derivative models of aircraft, in which tests are carried out both in a stream and without a stream in a wind tunnel, the model is installed in a movable support device using tensile weights and the holder, the model is oscillated with a fixed frequency and with small amplitude alternately relative to the axes Ox, Oy and Oz, the loads acting on the model and its angular position are measured in time, produced in reading inertial and weight loads, and then calculating static and complexes of non-stationary and rotational aerodynamic derivatives (Experimental studies and mathematical modeling of non-stationary aerodynamic characteristics of aircraft models. TsAGI proceedings - collection of articles. M., 2010, issue 2689, p.5- 6). The disadvantage of this method is that it also does not allow to determine static and non-stationary aerodynamic derivatives of aircraft models at non-zero gliding angles.

A prior art device is also known for determining static and non-stationary aerodynamic derivative models of aircraft, comprising a turntable in the working part of the wind tunnel, a stand on the turntable, a model holder with tensile weights mounted in the bearing assembly of the rack, a drive coupled by a rod to the holder, holder rotation angle sensor (G. S. Byushgens, R. V. Studnev, Aerodynamics of an airplane. Dynamics of longitudinal and lateral movement. M., Mechanical Engineering, 1979, p. 32-34). The disadvantage of the described device is the impossibility of testing when the model oscillates in the longitudinal channel and yaw at sliding angles not equal to zero, if the angle of attack of the model is not equal to zero, as well as the inability to test at sliding angles not equal to zero, in the entire range of angles of attack of the model with its oscillations along the roll.

Closest to the claimed technical solution is a device for determining static and non-stationary aerodynamic derivative models of aircraft, comprising a turntable in the working part of the wind tunnel, a stand on the turntable, a movable L-shaped frame, a model holder with tensile weights mounted in the bearing assembly of the frame, drive connected by rods to the frame and holder, angle sensors of rotation of the frame and holder (Experimental studies and mathematical modeling of unsteady rodinamicheskih characteristics of aircraft models, Trudy TsAGI -. a collection of articles, Moscow, 2010, edition of 2689, s.5-6).. The disadvantage of this device is that it also does not allow testing to determine the static and non-stationary aerodynamic derivatives of aircraft models at non-zero gliding angles.

The objective and technical result of the invention is the creation of a method and device for determining static and non-stationary aerodynamic derivative models of aircraft in the presence of a sliding angle in the entire range of angles of attack, which increases the safety of operation of the aircraft, in particular, prevents the occurrence of stalling of the aircraft and falling into a tailspin.

The solution of the problem and the technical result are achieved by the fact that in the method for determining static and non-stationary aerodynamic derivative models of aircraft, which consists in the fact that the tests are carried out both in a stream and without a stream in a wind tunnel, the model is installed in a movable support by means of tensors and a holder the device, the model is oscillated with a fixed frequency and small amplitude alternately with respect to the axes Ox, Oy and Oz, the loads acting on the model and its angles are measured in time position, subtract the inertial and weight loads, during the test, the model, together with the holder and the tensile weights, are rotated to fixed roll angles, the experimental results are processed together with vibrations relative to the Oy and Oz axes, and the values of static and unsteady aerodynamic derivatives are determined by the formulas

, $$C^{\alpha }=C_{\mathrm{one}}^{\omega z}\cos \gamma -C_{\mathrm{one}}^{\omega y}\sin \gamma$$

,

, $$C^{\beta }=C_{\mathrm{one}}^{\omega z}\sin s\gamma -C_{\mathrm{one}}^{\omega y}\cos \gamma$$

,

$$C^{\overline{\omega }y}+C^{\overline{\dot{\alpha }}}=C_2^{\omega z}\cos \gamma -\frac{l}{2b_a}{C}_2^{\omega y}\sin \gamma ,$$

, $$C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta =\frac{2b_a}{l}{C}_2^{\omega z}\sin \gamma +C_2^{\omega y}\cos \gamma$$

,

- комплекс продольных вращательной и нестационарной аэродинамических производных; $$C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta$$

- комплекс боковых вращательной и нестационарных аэродинамических производных, γ - угол поворота державки по крену, $$C_1^{\omega z}$$

- составляющая сигнала в фазе с углом колебаний модели при колебаниях относительно оси Oz, $$C_1^{\omega y}$$

- составляющая сигнала в фазе с углом колебаний модели при колебаниях относительно оси Oy, $$C_2^{\omega z}$$

- составляющая сигнала в фазе с угловой скоростью колебаний модели при колебаниях относительно оси Oz, $$C_2^{\omega y}$$

- составляющая сигнала в фазе с угловой скоростью колебаний модели при колебаниях относительно оси Oy, l - размах крыла модели, b_a - САХ модели.where C = C_y, C_x, m_x, m_y or m_z, C^α is the static derivative of the aerodynamic coefficient from the angle of attack, C^β - the static derivative of the aerodynamic coefficient from the slip angle, $$C^{\overline{\omega }y}+C^{\overline{\dot{\alpha }}}$$

 - a complex of longitudinal rotational and non-stationary aerodynamic derivatives; $$C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta$$

 - a complex of lateral rotational and non-stationary aerodynamic derivatives, γ is the angle of rotation of the holder along the roll, $$C_{\mathrm{one}}^{\omega z}$$

 - the component of the signal in phase with the angle of oscillation of the model during oscillations relative to the axis Oz, $$C_{\mathrm{one}}^{\omega y}$$

 - the component of the signal in phase with the angle of oscillation of the model during oscillations about the axis Oy, $$C_2^{\omega z}$$

 - the signal component in phase with the angular velocity of oscillations of the model during oscillations about the axis Oz, $$C_2^{\omega y}$$

 is the signal component in phase with the angular velocity of oscillations of the model with oscillations about the Oy axis, l is the wingspan of the model_a - SAH model.

The solution of the problem and the technical result are also achieved by the fact that in the device for determining static and non-stationary aerodynamic derivative models of aircraft, containing a turntable in the working part of the wind tunnel, a stand on the turntable, a movable L-shaped frame, a model holder with tensile weights mounted in the bearing unit of the frame, the drive connected by rods to the frame and holder, the angle sensors of rotation of the frame and holder, introduced the mechanism for remote installation of the holder, consisting of a housing mounted on the bearing assembly of the frame by means of bearings, an electric motor gearbox and an output shaft with an elastic gear disk mounted coaxially to the holder and connected to its free end, a pneumatic brake of the disc mounted in the housing and covering the elastic gear disk, an additional installation angle sensor the holder along the roll, which is extended from the axis of the holder and connected with the gear wheel, the clamp lever mounted on the outer surface of the mechanism body with the possibility of fixing the relative body but the frame and connecting rod drive.

The essence of the proposed method and device for determining static and non-stationary aerodynamic derivative models of aircraft is illustrated in figures 1-6, which show:

figure 1 - diagram of the tests to determine the static and non-stationary aerodynamic derivative models of aircraft with oscillations relative to various associated axes;

figure 2 - diagram of the inventive device for determining static and non-stationary aerodynamic derivative models of aircraft;

figure 3 is a diagram of a mechanism for remote installation of the holder at a given angle of heel;

figure 4 is a graph of the dependence of the angles of attack α and slip β from the angle of rotation of the circle in the working part of the wind tunnel θ and the angle of heel of the holder γ;

5, 6, 7 are graphs of the dependences of the static and non-stationary aerodynamic derivatives of the model of a triangular wing on the angle of attack for various values of the angle of slip.

The list of used items in the description of the invention.

1. The turntable in the working part of the wind tunnel.

2. Movable L-shaped frame.

3. The stand.

4. Thrust.

5. The drive.

6. The holder.

7. Tennis weights.

8. The mechanism for remote installation of the holder.

9. Aircraft model.

10. The sensor angle of rotation of the frame.

11. The bearing assembly of the frame.

12. The output shaft.

13. Electric gear motor.

14. Elastic gear wheel.

15. Roll angle sensor.

16. Case.

17. Pneumatic brake disc.

18. Bearing.

19. Lever-clamp.

20. Sensor angle of rotation of the holder.

The method for determining static and non-stationary aerodynamic derivative models of aircraft consists in the fact that tests are carried out both in a stream and without a stream in a wind tunnel, the model is installed in a movable support device by means of tens weights and a holder, the model is oscillated with a fixed frequency and low amplitude alternately relative to axes Ox, Oy and Oz, measure the loads acting on the model and its angular position in time, subtract the inertial and weight loads. To do this, the device is sequentially assembled in a configuration for conducting studies of derivatives of a model when it fluctuates with respect to one of the associated axes (Fig. 1). A model of the aircraft 9 is installed in a movable supporting device - holder 8 with tenzovy 7 (Fig.2). Using the mechanism for remote installation of the holder 8, the model is rotated by a fixed roll angle γ _i , using a turntable in the working part of the wind tunnel 1, model 9 is set at an angle θ _i to the flow axis of the wind tunnel (Fig. 2). Drive 5 is adjusted to the desired values of amplitude A and circular frequency ω and oscillate the movable L-shaped frame 2 according to the harmonic law

$$\Delta \theta (t)=A\sin \omega t.(\mathrm{one})$$

The magnitude of the amplitude of the oscillations is small and equal to 2 ÷ 3 °. Without flow in the wind tunnel for sixteen periods of vibration, a tensor 7 is measured and five components of the loads acting on the model Y, Z, M _x , M _y , M _{z are} recorded, as well as the readings of the angle sensors of the holder 20 and the frame 10. Studies are carried out for several angles θ _i . The value of inertial and weight loads is determined. Then turn on the flow in the wind tunnel and these operations are repeated. Inertial and weight loads are subtracted from the loads received in the stream. Then, the dependences of the static and non-stationary aerodynamic derivatives of the model are obtained using the algorithm described below.

To conduct tests at given average values of the angle of attack α _i and slip β _{i, the} model must be installed at the corresponding angles γ _i and θ _i . The relationship between the values of these angles is described by a system of equations

$$\begin{array}{c}tg\alpha =tg\theta \cos \gamma \\ \sin \beta =\sin \theta \sin \gamma \end{array}(2)$$

When solving this system of equations, the required values of the rotation angles of the circle θ _i and the holder γ _i are obtained for the given values of the angle of attack and slip according to the following formulas

$$\begin{array}{l}{\cos }^2\theta ={\cos }^2\alpha +{\cos }^2\beta (3)\\ {\sin }^2\gamma =\frac{\mathrm{one}-{\cos }^2\beta }{\mathrm{one}-{\cos }^2\alpha {\cos }^2\beta }\end{array}$$

Graphically shown dependencies are presented in figure 4. When conducting research, the necessary values of the angles θ and γ at the given angles α and β are calculated in real time on a computer.

When you rotate the model with tensile weights on the roll when fluctuating in pitch and yaw, the angular velocity of rotation of the model has a projection simultaneously on two axes of the associated coordinate system of the model - ω _z and ω _y (Fig. 2). In this regard, the experimental results for oscillations about the Oy and Oz axes are processed together - only the simultaneous processing of the oscillation results in pitch and yaw with the subsequent solution of the corresponding linear system of equations allows us to obtain the required dependences of the static and non-stationary aerodynamic derivatives of the model.

Consider the small pitch fluctuations of the model. Let the angle of rotation of the installation frame change according to the law

$$\Delta \theta =\in \sin \omega t,(\mathrm{four})$$

Where ∈ ₀ << 1 is the oscillation amplitude, ω = 2πf is the frequency. Then small changes in the angles of attack and glide of the model relative to average values can be represented by the formulas

$$\begin{array}{c}\Delta \alpha (t)=\Delta \theta (t)\cos \gamma ,\\ \Delta \beta (t)=\Delta \theta (t)\sin \gamma .\end{array}(5)$$

The components of the angular velocity of the model can be expressed as follows:

$$\begin{array}{c}{\omega }_y=\Omega (t)\sin \gamma \\ {\omega }_z=\Omega (t)\cos \gamma ,\end{array}(6)$$

.Where $$\Omega =\Delta \theta ={\in }_0\omega \cos \omega t$$

.

Consequently, in the presence of a rotation of the model along the roll angle during fluctuations in pitch in the associated coordinate system, angular rotational velocities of the model ω _y and ω _z arise, in contrast to the case γ = 0, when ω _y = 0.

Expressions for the time derivatives of the angles of attack and slip can be found using the kinematic relations:

$$\begin{array}{c}\dot{\alpha }={\omega }_z-({\omega }_x\cos \alpha -{\omega }_y\sin \alpha )tg\beta ,\\ \dot{\beta }={\omega }_x\sin \alpha +{\omega }_y\cos \alpha .\end{array}(7)$$

Given (6), we can obtain

$$\begin{array}{c}\dot{\alpha }=\Omega (t)(\cos \gamma +\sin \gamma \sin \alpha tg\beta ),\\ \dot{\beta }=\Omega (t)\sin \gamma \cos \alpha .\end{array}(8)$$

Therefore, in the linear approximation, taking into account (5), (6) and (8), when fluctuating in pitch, the aerodynamic coefficients can be represented as follows

$$\begin{array}{l}C={\mathrm{<figure-callout\; id="0"\; label="C"\; filenames="00000052.png,00000054.png"\; state="\{\{state\}\}">C</figure-callout>}}_0+C^{\alpha }\Delta \theta \cos \gamma +C^{\beta }\Delta \theta \sin \gamma +C^{\overline{\dot{\alpha }}}\frac{b_a}{V}\Omega (\sin \alpha tg\beta \sin \gamma +\cos \gamma )+\\ +C^{\overline{\dot{\beta }}}\frac{l}{2V}\Omega \sin \gamma \cos \alpha +C^{\overline{\omega }y}\frac{l}{2V}\Omega \sin \gamma +C^{\overline{\omega }z}\frac{b_a}{V}\Omega \cos \gamma =\\ =C_0(C^{\alpha }\cos \gamma +C^{\beta }\sin \gamma )\Delta \theta +[(C^{\overline{\omega }z}+C^{\overline{\dot{\alpha }}})]\frac{b_a}{V}\cos \gamma +\\ (C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C\overline{\dot{\alpha }}\frac{2b_a}{l}\sin \alpha tg\beta )\frac{l}{2V}\sin \gamma ]\Omega ,\end{array}$$

where C = C _y , C _z , m _x , m _y or m _z .

Thus, each channel of tensile weights with small pitch oscillations perceives a certain average value of C ₀ and signals in phase with a reference signal Δθ (t) and in phase with a signal Ω (t) = Δθ (t). The component of the signal in phase with the reference signal is proportional

$$C_{\mathrm{one}}^{\omega z}=C^{\alpha }\cos \gamma +C^{\beta }\sin \gamma .(9)$$

The component of the signal in phase with angular velocity (phase advance by π / 2 is expressed as follows

$$C_2^{\omega z}=(C^{\overline{\omega }z}+C^{\overline{\dot{\alpha }}})\frac{b_a}{V}\cos \gamma +(C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta )\frac{l}{2V}\sin \gamma .(10)$$

0 в результате эксперимента при вынужденных колебаниях по тангажу могут быть выделены сложные комплексы производных, описываемые выражениями (9) и (10).Thus, for γ $$\ne$$

0 as a result of an experiment with forced pitch oscillations, complex complexes of derivatives described by expressions (9) and (10) can be distinguished.

Let us now analyze the kinematics of the model with yaw fluctuations. In this case, the installation frame is rotated so that its vibrations change the yaw angle of the model. Moreover, its small fluctuations (4) lead to the following changes in the instantaneous values of the angles of attack and slip relative to the average values determined by the expression (2)

$$\begin{array}{c}\Delta \alpha (t)=-\Delta \theta (t)\sin \gamma ,\\ \Delta \beta (t)=\Delta \theta (t)\cos \gamma .\end{array}(\mathrm{eleven})$$

The angular velocity components are as follows

$$\begin{array}{c}{\omega }_y=\Omega (t)\cos \gamma \\ {\omega }_z=-\Omega (t)\sin \gamma \end{array}(12)$$

The expressions for the derivatives of the angles of attack and slip in the case of yaw oscillations are determined from the above formulas (12) taking into account the kinematic relations (7):

$$\begin{array}{c}\dot{\alpha }=\Omega (t)(-\sin \gamma +\cos \gamma \sin \alpha tg\beta ),\\ \dot{\beta }=\Omega (t)\cos \gamma \cos \alpha .\end{array}(13)$$

In the linear approximation, the coefficients of forces and moments acting on the model during yawing vibrations, taking into account (11), (12) and (13), can be represented as:

$$\begin{array}{l}C=C_0(-C^{\alpha }\sin \gamma +C^{\beta }\cos \gamma )\Delta \theta +[-(C^{\overline{\omega }z}+C^{\overline{\dot{\alpha }}})]\frac{b_a}{V}\sin \gamma +\\ (C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C\overline{\dot{\alpha }}\frac{2b_a}{l}\sin \alpha tg\beta )\frac{l}{2V}\cos \gamma ]\Omega .\end{array}$$

Thus, by analogy with the case of pitch oscillations, for small fluctuations in yaw, each channel of the tensile weights also perceives a certain average value of C ₀ and signals in phase with a reference signal Δθ (t) and in phase with a signal Ω (t) = Δθ (t ):

$$C_{\mathrm{one}}^{\omega y}=-C^{\alpha }\sin \gamma +C^{\beta }\cos \gamma .(\mathrm{fourteen})$$

Taking into account expressions (9) and (14,), solving the system of equations for finding the derivatives C ^α and C ^β , we obtain

$$C_2^{\omega y}=-(C^{\overline{\omega }z}+C^{\overline{\dot{\alpha }}})\frac{b_a}{V}\sin \gamma +(C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta )\frac{l}{2V}\sin \gamma ,(\mathrm{fifteen})$$

- составляющая сигнала в фазе с углом колебаний модели при колебаниях относительно оси Oz, $$C_1^{\omega y}$$

- составляющая сигнала в фазе с углом колебаний модели при колебаниях относительно оси Oy. Коэффициент $$C_1^{\omega z}$$

получен методом линейной регрессии при колебаниях модели по тангажу для заданных средних значений углов атаки и скольжения, а коэффициент $$C_1^{\omega y}$$

- при колебаниях по рысканию.where C ^α is the static derivative of the aerodynamic coefficient of the angle of attack, C ^β is the static derivative of the aerodynamic coefficient of the angle of slip, $$C_{\mathrm{one}}^{\omega z}$$

- the component of the signal in phase with the angle of oscillation of the model during oscillations relative to the axis Oz, $$C_{\mathrm{one}}^{\omega y}$$

- the signal component in phase with the angle of oscillation of the model during oscillations about the axis Oy. Coefficient $$C_{\mathrm{one}}^{\omega z}$$

obtained by linear regression when the model fluctuates in pitch for a given average values of the angle of attack and slip, and the coefficient $$C_{\mathrm{one}}^{\omega y}$$

- with fluctuations in yaw.

Similarly, taking into account expressions (10) and (15), one can find complexes of derivatives

$$C^{\overline{\omega }y}+C^{\overline{\dot{\alpha }}}=C_2^{\omega z}\cos \gamma -\frac{l}{2b_a}{C}_2^{\omega y}\sin \gamma ,$$

. $$C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta =\frac{2b_a}{l}{C}_2^{\omega z}\sin \gamma +C_2^{\omega y}\cos \gamma$$

.

- комплекс продольных вращательной и нестационарной аэродинамических производных; $$C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta$$

- комплекс боковых вращательной и нестационарных аэродинамических производных, $$C_2^{\omega z}$$

- составляющая сигнала в фазе с угловой скоростью колебаний модели при колебаниях относительно оси Oz, $$C_2^{\omega y}$$

- составляющая сигнала в фазе с угловой скоростью колебаний модели при колебаниях относительно оси Oy, l - размах крыла модели, b_a - САХ модели.In this expression $$C^{\overline{\omega }z}+C^{\overline{\dot{\alpha }}}$$

- a complex of longitudinal rotational and non-stationary aerodynamic derivatives; $$C^{\overline{\omega }y}+C^{\overline{\dot{\beta }}}\cos \alpha +C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\sin \alpha tg\beta$$

- a complex of lateral rotational and non-stationary aerodynamic derivatives, $$C_2^{\omega z}$$

- the signal component in phase with the angular velocity of oscillations of the model during oscillations about the axis Oz, $$C_2^{\omega y}$$

is the signal component in phase with the angular velocity of oscillations of the model with oscillations about the Oy axis, l is the wing span of the model, b _a is the SAX of the model.

Processing together the experimental results for pitch and yaw fluctuations, one can find all the necessary complexes of stationary and non-stationary derivatives for given average values of the angle of attack and slip.

During roll oscillations for the installation angle γ ≠ 0, only one component of the angular velocity of the model motion is nonzero in the same way as in the case γ = 0

. $${\omega }_x=\Omega =\Delta \theta ={\in }_0\omega \cos \omega t$$

.

Those. for such oscillations, an initial rotation by a certain constant angle of heel does not lead to additional relationships between complexes of aerodynamic derivatives.

The expressions for the derivatives of the angles of attack and slip are of the form

, $$\dot{\alpha }=-\Omega (t)\cos \alpha tg\beta$$

,

. $$\dot{\beta }=\Omega (t)\sin \alpha$$

.

составляющей сигнала тензовесов, опережающий по фазе на π/2 опорный сигнал, может быть выражен следующим образомConsequently, in the case of small roll oscillations of the model, the proportionality coefficient $$C_2^{\omega x}$$

component of the signal of the tensile weights, which is ahead of the phase by π / 2 of the reference signal, can be expressed as follows

$$C_2^{\omega x}=C^{\overline{\omega }x}+C^{\overline{\dot{\beta }}}\sin \alpha -C^{\overline{\dot{\alpha }}}\frac{2b_a}{l}\cos \alpha tg\beta .$$

Therefore, it is possible to investigate the dependence of roll damping on the slip angle without solving additional systems of linear equations.

The proposed method is implemented using a device for determining static and non-stationary aerodynamic derivative models of aircraft, assembled in one of three options for oscillation of the model relative to one of the associated axes (figure 1). The device comprises a turntable 1 in the working part of the wind tunnel (Fig. 2), a stand 3 on the turntable, a movable L-shaped frame 2, a holder 6 of the model with ten weights 7 mounted in the bearing assembly of the frame 11, the drive 5 connected by rods 4 with frame or holder (depending on the configuration of the device), the angle sensors of the frame 10 and holder 6. When the model fluctuates in pitch, the L-shaped frame 2 is installed in the vertical plane (figure 1), with yaw fluctuations, the movable L-shaped frame 2 translates to horizontal position e, this uses a rack 3 of greater height. When the model oscillates along the roll, the rod from the drive is attached not to the L-shaped frame 2, but to the lever-clamp 19 of the mechanism 8. For the remotely controlled rotation of the holder to a predetermined roll angle, the device uses the mechanism for remote installation of the holder 8, consisting of a housing 16 installed on the bearing assembly of the frame 11 by means of bearings 18 (Fig. 3), an electric motor gearbox 13 and an output shaft 12 with an elastic gear disk 14 mounted coaxially to the holder 6 and connected to its free end, a pneumatic brake of a disk 17 installed in the housing and covering the elastic gear wheel, an additional gauge of the holder angle of inclination along the roll 15, which is extended from the axis of the holder and connected to the gear wheel, the clamp lever 19 mounted on the outer surface of the mechanism body with the possibility of fixing the case relative to the frame and connecting it with driven. An additional sensor angle of installation of the holder on the roll 15 is used to measure the angle of rotation of the holder 6 relative to the housing 16.

The device operates as follows. The device is assembled in the desired configuration for studies of the aerodynamic derivatives of the model when it fluctuates relative to one of the associated axes (figure 1). During the pitch and yaw tests, the drive 5 by means of the thrust 4 causes the movable L-shaped frame 2 to perform harmonic periodic oscillations with a given small amplitude and frequency relative to the axis of the rack 3. The housing of the mechanism 8 is fixed relative to the bearing assembly of the frame 11 by a lever-clamp 19. In doing so the model of the aircraft 9, mounted on a holder 6 and a tensile 7, also oscillates about the axis of the rack. When conducting roll tests, the movable L-shaped frame 2 is fixed relative to the rack 3. The case of the mechanism 8 is released and connected using the rod 4 and the clamping lever 19 to the drive 5. In this case, the model 9 with the tensile weights 7 and the holder 6 oscillates relative to the axis of the holder . To rotate the model through an angle θ _i , a turntable 1 is used, to rotate the holder through an angle γ _i , the mechanism for remote installation of the holder 8 is used. The forces and moments acting on the model are measured using a ten-weight 7. The rotation of the device frame is measured by an angle sensor 10, the angle of rotation the holder - with the sensor 20. The holder 6 with the model 9 is rotated to the required roll angle by the mechanism 8. In this case, the air brake 17 is first turned off and unlocks the gear wheel 14 relative to the housing 16. The electric gear motor 13 is turned on and rotated holder 6 through the output shaft 12. In this case, the angle of installation of the holder on the roll is measured by the sensor 15. When the holder reaches the desired installation angle, the gear motor 13 is turned off, compressed air is supplied to the air brake 17, it blocks the gear wheel 14, fixing the holder 6 from turning relative to the case of the mechanism 16. The lever-clamp 19 in the case of oscillation of the model in pitch and yaw is shifted so that when tightening it simultaneously compresses the outer surfaces of the body of the mechanism 16 and the bearing assembly of the frame 11, rigidly fixing them together. When the model fluctuates along the roll, the lever-clamp 19 is completely shifted to the housing 16 and is clamped on it. A link 4 from the drive 5 is attached to the lever. In this case, the mechanism 8, turning on the bearings 18 relative to the frame 2, transmits small angular vibrations to the holder 6.

Thus, the expected technical result is achieved, namely, it becomes possible to conduct tests to determine the static and non-stationary aerodynamic derivative models of aircraft at gliding angles other than zero in the entire range of angles of attack.

при колебаниях по тангажу. На фиг.5-7 показаны зависимости статических и нестационарных аэродинамических производных модели треугольного крыла от угла атаки C_y(α), m_z(α), $$(m_z^{{\varpi }_z}+m_z^{\overline{\dot{\alpha }}})(\alpha )$$

, $$(m_x^{{\varpi }_x}+m_x^{\overline{\dot{\beta }}}\sin \alpha )(\alpha )$$

, полученные при различных значениях угла скольжения. Можно отметить существенное влияние величины угла скольжения на аэродинамические производные треугольного крыла.The proposed method and device for determining static and unsteady aerodynamic derivative models of aircraft were used to test the model of a triangular wing with elongation λ = 1.5 with sweep χ≈70 ° and root chord b _a = 1.2 m at a flow velocity V _∞ = 25 m / s, which corresponds to the Reynolds number Re = 2.0 · 10 ⁶ in the root chord. Center model oscillation located at χ _T - 0.5 b _a. The experiments were carried out in the range of angles of attack α = 0 ÷ 60 ° for slip angles β = 0, 5, 10, and 15 °. The amplitude of the oscillations was Δθ = 3 °, the frequency f = 1.5 Hz, which corresponds to the dimensionless circular frequency $$\overline{\omega }=\frac{2\pi f{b}_a}{V_{\infty }}=0.18$$

with pitch fluctuations. Figure 5-7 shows the dependences of the static and non-stationary aerodynamic derivatives of the model of a triangular wing on the angle of attack C _y (α), m _z (α), $$(m_z^{{\varpi }_z}+m_z^{\overline{\dot{\alpha }}})(\alpha )$$

, $$(m_x^{{\varpi }_x}+m_x^{\overline{\dot{\beta }}}\sin \alpha )(\alpha )$$

obtained at different values of the angle of slip. We can note a significant effect of the slip angle on the aerodynamic derivatives of the triangular wing.

Thus, it is shown that this technical solution allows the determination of static and non-stationary aerodynamic derivatives of aircraft models in the presence of a sliding angle in the entire range of angles of attack. This increases the safety of operation of the aircraft, in particular, helps prevent the occurrence of stalling of the aircraft and falling into a tailspin.

Claims (2)

1. A method for determining static and non-stationary aerodynamic derivative models of aircraft, which consists in the fact that the tests are carried out both in a stream and without a stream in a wind tunnel, the model is installed in a movable support device by means of tensors and a holder, the model is oscillated with a fixed frequency and small amplitude alternately relative to the axes Ox, Oy and Oz, measure the loads acting on the model and its angular position in time, subtract the inertial and weight loads, distinguish in that during the test the model, together with the holder and the tensile weights, is rotated at fixed roll angles, the experimental results are processed together with oscillations about the Oy and Oz axes, and the values of static and non-stationary aerodynamic derivatives are determined by the formulas

,

,

,

,
where C = C _y , C _x , m _x , m _y or m _z , C ^α is the static derivative of the aerodynamic coefficient from the angle of attack, C ^β is the static derivative of the aerodynamic coefficient from the angle of slip,

- a complex of longitudinal rotational and non-stationary aerodynamic derivatives;

- a complex of lateral rotational and non-stationary aerodynamic derivatives, γ is the angle of rotation of the holder along the roll,

- the component of the signal in phase with the angle of oscillation of the model during oscillations relative to the axis Oz,

- the component of the signal in phase with the angle of oscillation of the model during oscillations about the axis Oy,

- the signal component in phase with the angular velocity of oscillations of the model during oscillations about the axis Oz,

is the signal component in phase with the angular velocity of oscillations of the model with oscillations about the Oy axis, l is the wing span of the model, b _a is the average aerodynamic chord (SAX) of the model. 2. A device for determining static and non-stationary aerodynamic derivative models of aircraft, comprising a turntable in the working part of the wind tunnel, a stand on the turntable, a movable L-shaped frame, a model holder with tensile weights mounted in the bearing assembly of the frame, a drive connected with rods with frame and holder, angle sensors of rotation of the frame and holder, characterized in that a mechanism for remote installation of the holder consisting of a housing mounted on the bearing assembly of the frame by means of bearings, an electric motor-reducer and an output shaft with an elastic gear disk mounted coaxially to the tool holder and connected to its free end, a pneumatic brake of the disk installed in the housing and covering the elastic gear wheel, an additional sensor of the holder installation angle along the roll, which is removed from the axis of the holder and is connected with the gear wheel, a clamp lever mounted on the outer surface of the mechanism housing with the possibility of fixing the housing relative to the frame and connecting the rod to the drive.

Images